FA (factory automation) robots operate in the situation where the robots are spatially isolated from people (i.e., in an area where no person is present) for its efficient operation and safety ensuring. Some robots, such as a building-cleaning robot, take the form of operating in the situation where the robots are temporally isolated from people (i.e., during a period of time when no person is present in the area) for efficient operation and safety ensuring. The robots which operate in the area, in which people are living, to relieve people from their loads in daily life or assist people in their daily life, in other words, the robots which can coexist with people, will be considered more important in the future. The robots include, for example, robots working in a hospital such as a robot which autonomously travels to carry loads or a robot which travels while cleaning the floor during a period of time when people are present in the area.
That kinds of robots may collide with persons while the robots are traveling; therefore, it is required for the robots to travel while avoiding collisions with any obstacles including persons to ensure safety of people.
For example, JP 2001-154706 A (Patent Literature 1) proposes a system of avoiding a collision by giving a virtual repulsive potential to an obstacle in a moving space of a robot and having the robot receive a virtual repulsive force responded to the repulsive potential.
In addition, assuming that the robot coexists with people, it is desirable that the operation of the robot or the purpose of the operation of the robot is easily understood by people.
For example, JP 2004-118469 A (Patent Literature 2) proposes a system of causing a robot to present the direction of searching for an obstacle or the next direction of travel to a person through rotation of its head or movement of its eyes by having rotatably attached a display device which imitates eye movements to the head of the robot.